Hi,
this behaviour might be because of some Windows security setting.
Is this your own computer or a work one? If work then they might have set up
a policy which does not let you switch the macro security level.
One way would be to not change to a low security level. This should be
avoided anyway since it brings a security risk. Instead try to digitially
sign your project. You can either do this by yourself with selfcert.exe, or
you can buy one from a trusted source. If you do it yourself the macro
warning will come up ones when run for the first time, but if the users
enable the project for all times they will not receive the warning again. If
you buy one they will not be bothered with it at all. Another solution would
be to run the access install in sandbox mode, but I would suggest signing
your code.
HTH
Good luck